<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

  <div id="app"></div>


  <script src="https://unpkg.com/vue@next"></script>
  <script>
      Vue.createApp({
          template: `
          <div>
               <h2>{{message}}</h2>
               <h2>{{countNum}}</h2>
               <button @click="incr">+1</button>
               <button @click="decr">+1</button>
          </div>
          `,
          data: function () {
              return {
                message: 'Hello World',
                countNum: 100,
              }
          },
          methods: {
              incr(){
                  this.countNum++;
              },
              decr(){
                  this.countNum--;
              },
          }
      }).mount('#app');
  </script>
</body>
</html>